The moat is the one between communications and applications. Communications say things, and applications interact with things. There are crossover areas, but something like email is designed and overwhelmingly used to say things, while websites and apps are overwhelmingly designed and used to interact with things....The moat between communication and action is important because it makes it very clear what certain tools are capable of, which in turn lets them be trusted and used properly..

What Google wants to do is bridge that moat, essentially to allow applications to run inside emails, limited ones to be sure, but by definition the kind of thing that belongs on the other side of the moat.....Which brings us to the motive.

AMP is, to begin with, Google exerting its market power to extend its control over others’ content. Facebook is doing it, so Google has to. Using its privileged position as the means through which people find a great deal of content, Google is attempting to make it so that the content itself must also be part of a system it has defined.

“AMP started as an effort to help publishers, but as its capabilities have expanded over time, it’s now one of the best ways to build rich webpages,” it writes in the blog post announcing the AMP for Gmail test. No, it isn’t. AMP is a way to adapt and deliver, on Google’s terms, real webpages built with real tools.AMP for email is just an extension of that principle. People leave Gmail all the time to go to airline webpages, online shops, social media, and other places. Places that have created their own user environments, with their own analytics, their own processes that may or may not be beneficial or even visible to Google. Can’t have that!

And there's more of the Devils advocate "Facts" further down

Personally I cannot see anything in it for myself The Ad blocker Apps will be working overtime!
Only thing we can hope for is that Google Give us an option (Setting) to Refuse/disable it
Could also Let Spam and False News/ad links back in through this door Haven't factored that in Google?

One thing I've learnt over the years is that making email "richer" in terms of features has always brought new security challenges. My worry would be that new levels of interaction like this might make it easier for unsuspecting users to fall for a phishing attack or scam.

We'll have to wait and see, of course, once the feature begins to roll out. But we know right now that online criminals are nothing if not inventive, and inevitably seize the opportunities brought by new technologies to pull the wool over unsuspecting users' eyes.

Email has been around for nearly half a century and there are some things about it that are looking decidedly dated. In particular, its approach to privacy and security are decidedly mid-twentieth century.